The invention relates to a device for separating a radiation beam into its different wavelength components. The beam emerges from an optical fiber, and is separated by a reflection grating.
Such a device is known, for example, from an article by K. Aoyama et al entitled "Low-loss optical demultiplexer for WDM systems in the 0.8-.mu.m wavelength region" (Applied Optics, Vol. 18, No. 16, pages 2834-2836, Aug. 15, 1979). In the known device the radiation beams which emerge from the optical fiber are aimed at the reflection grating by a lens system. The angle at which the radiation beams are reflected by the grating depends on the wavelengths of the beams. After passing through the lens system, the radiation beams thus separated are routed to a plurality of output optical fibers. Each of the output fibers corresponds to a beam of wavelength .lambda..sub.1, .lambda..sub.2, . . . .lambda..sub.n, respectively, which is reflected by the grating at an angle .alpha..sub.1, .alpha..sub.2, . . . .alpha..sub.n, respectively.
It is a disadvantage of the known device that only radiation beams of wavelengths which are comparatively close to each other can be separated.